Yeah it can happen early, im not even 6 weeks yet and ive been having it more than normal for over a week now. Its the increase in progesterone i think that weakens the muscles at the top of your stomach and let the acid out. You can take over the counter antacids like gaviscon and rennies and tums etc but check with your doc as they may be able to prescribe something.
and no, it's not too early. It happens. for some reason when I was pregnant with both my son's I had horrible heartburn requiring 2 OTC Prilosec's a day just to control.
it started around 8 weeks with my 2nd son. Something about the body chemistry changing with pregnancy or so it seemed that way to me. :)
You can take Nexium, or even the Purple Pill, Prilosec which is OTC and safe in pregnancy according to the OB's I had with my pregnancies.
here's a site with info on ways to prevent it, treat it, and other things
http://heartburn.about.com/od/preventingheartburn/a/pregnancyhrtbrn.htm
and another
http://www.webmd.com/heartburn-gerd/guide/treating-heartburn-over-counter-medicine
its just really early to get it dont you think??????
call the doctor.... when i was preg i got i really bad and nothing worked so they actually perscribed me nexium and it really helped!! good luck